Lately my truck hasn't had any heat. I have yet to diagnose it but last night I heard it making some funny sounds. This morning I checked under the hood and the a/c compressor keeps kicking on even though the ac is not turned on. Any one have any idea why this would happen? It's an 01 4banger if that helps any.

 

there are settings on your heater controll that will run the ac comp (defrost) this is normal your clicking on and off may be a low charge. the compressor running in deftost helps remove moisture from the inside. Try back flushing yor heater core for your lack of heat